More changes would be needed than direct uniform scaling - .22lr is rimfire, whereas .45acp is centerfire, for example, and their aspect ratios are different. The mass and strength of uniformly scaled-down parts also might not match the recoil and pressure provided by the smaller round, and might result in failure to reliably cycle the action or the gun bursting if the mismatch is too much.

The thing I remember most about this book is the heroic American Mary Sue rescuing an Icelandic damsel in distress from a traumatic sexual assault by Soviet soldiers, and then immediately afterwards she falls in love with him and they have sex in a hot spring or something. Standard conservative male military-nerd wish-fulfillment pulp fantasy written by a guy whose main protagonists are all thinly-veiled self-insertions.

That said, as a fellow nerd, I love it when Clancy tells me all the little details about a submarine, and it’s a fun read. But I wouldn’t call it good.